You're confusing two different things, setting a per core frequency is NOT the same thing as setting a per core multiplier. What you can't do is set your cores to run at specifically 4800Mhz, but as the video I provide proves, you can set a multiplier for each core. While the multiplier achieves an almost identical result, it is still an entirely different method of overclocking. Setting the per core frequency was done via changing the BUS speed, not the multiplier.
Here is that video again showing the Gigabyte Z370 Gaming 7 bios.
0:29 shows the ability to set per core multipliers. Also, there are several reviewers who set per core overclocks via multiplier. Tek Syndicate is one, they talk about it in that other video I linked previously Running the first 2 cores at 5.1GHz and cores 3-6 at 4.9Ghz to keep temps down. And I know that lab51 website did it too in their review that they posted before the NDA was lifted.
Not only that, but the article you linked does not talk about end user overclocking. It
only says that Intel will no longer "disclose" the per core turbo frequency. Which isn't true because they did exactly that. There is even the chart for it in the article. It's possible Intel is saying they are no longer going to "disclose" each individual cores clock speed, and aren't violating that by giving a range like they do. With Single Core, 2-3 Core, 4-5 Core and All Core. Instead of the frequency for each core 1-6.
But the per core Turbo frequency is still changeable by the user, so longer as their motherboard supports it.